The ability to access emergency response services by dialing a reserved emergency telephone number, such as 911 in the United States, is a vital component of public safety and emergency preparedness. In the United States, the Federal Communications Commission (FCC) has established a set of rules and regulations that require mobile communication providers to deliver enhanced emergency services to their subscribers. In particular, mobile communication providers are required to provide a current location of a 911 caller to emergency services.
There are also many other situations where it is useful to know the location of a device. For example, certain device applications may provide services that depend on device location. As another example, advertising may be tailored to the current location of a device user.
In some cases, the location of a mobile device can be determined and reported by the mobile device itself, based on global positioning system (GPS) data. In these cases, the mobile device provides geographical coordinates of its location to the mobile communication provider. The mobile communication provider or associated entities can use this information to determine a street address, and may provide the street address to emergency services. However, GPS is not always accurate, particularly in locations with poor visibility of the sky such as many cities.